Force Measurement System Having Inertial Compensation

• US 20120271565A1
• Filed: 04/20/2011
• Published: 10/25/2012
• Est. Priority Date: 04/20/2011
• Status: Active Grant

• Current Assignee: Bertec Corporation
• Original Assignee: Bertec Corporation
• Inventors: Berme, Necip, Guler, Hasan C.
• Granted Patent: US 8,315,822 B2
• Time in Patent Office: Days
• US Class Current: 702/41
• CPC Class Codes: A61B 2562/0219 Inertial sensors, e.g. accelerometers, gyroscopes, tilt switches
• CPC Class Codes: A61B 5/1036 Measuring load distribution, e.g. podologic studies
• CPC Class Codes: A61B 5/112 Gait analysis
• CPC Class Codes: A61B 5/224 Measuring muscular strength
• CPC Class Codes: G01L 5/16 for measuring several components of force
• CPC Class Codes: G01M 1/122 Determining position of centre of gravity

Abstract

A force measurement system having inertial compensation includes a force measurement assembly with at least one accelerometer configured to measure the acceleration thereof. According to one aspect of the invention, the force measurement system additionally includes at least one angular velocity sensor configured to measure the angular velocity of the force measurement assembly. According to another aspect of the invention, the force measurement system additionally includes a data processing device with a computer-readable medium loaded thereon that is configured to execute a calibration procedure for determining the inertial parameters of the force measurement assembly by utilizing the measured acceleration of the force measurement assembly while the force measurement assembly is subjected to a plurality of applied linear and/or rotational motion profiles. According to still another aspect of the invention, the at least one accelerometer is disposed on the force transducer.

Claims

1. A force measurement system having inertial compensation, the force measurement system comprising:

a force measurement assembly configured to receive a subject, the force measurement assembly including;

a surface for receiving at least one portion of the body of the subject;

at least one force transducer, the at least one force transducer configured to sense a measured quantity and output a signal that is representative of forces and/or moments being applied to the surface of the force measurement assembly by the subject;

at least one accelerometer configured to measure the acceleration of the force measurement assembly;

at least one angular velocity sensor configured to measure the angular velocity of the force measurement assembly; and

a data processing device operatively coupled to the force measurement assembly, the data processing device configured to receive the signal that is representative of the forces and/or moments being applied to the surface of the force measurement assembly by the subject and to convert the signal into output forces and/or moments, the data processing device being configured to receive the acceleration and the angular velocity measured by the at least one accelerometer and the at least one angular velocity sensor, respectively, and the data processing device further being configured to use the acceleration and the angular velocity measured by the at least one accelerometer and the at least one angular velocity sensor, respectively, to compute inertial forces and moments, and to determine corrected externally applied forces by computing the mathematical difference between the computed inertial forces and the output forces, and/or to determine corrected externally applied moments by computing the mathematical difference between the computed inertial moments and the output moments so as to improve the measurement accuracy of the forces and/or moments being applied to the surface of the force measurement assembly by the subject.

2. The force measurement system according to claim 1, wherein the data processing device computes the inertial moments as a function of the angular velocity measured by the at least one angular velocity sensor, as a function of an angular acceleration of the force measurement assembly, and as a function of an inertia matrix that is determined during a calibration procedure.

3. The force measurement system according to claim 2, wherein the data processing device computes the angular acceleration of the force measurement assembly by solving a plurality of kinematic equations using the acceleration and the angular velocity measured by the at least one accelerometer and the at least one angular velocity sensor, respectively.

4. The force measurement system according to claim 1, wherein the at least one angular velocity sensor comprises a multi-component angular velocity sensor that is capable of measuring angular velocities of the force measurement assembly about multiple rotational axes.

5. The force measurement system according to claim 4, wherein the data processing device computes the inertial moments as a function of the angular velocities measured by the multi-component angular velocity sensor, as a function of an angular acceleration of the force measurement assembly, and as a function of an inertia matrix that is determined during a calibration procedure.

6. The force measurement system according to claim 1, wherein the at least one force transducer comprises a plurality of force transducers for sensing measured quantities that are representative of multi-dimensional forces and moments being applied to the surface of the force measurement assembly by the subject.

7. The force measurement system according to claim 6, wherein the at least one accelerometer comprises a plurality of accelerometers so as to enable multi-axis acceleration of the force measurement assembly to be determined, thereby compensating for the movement of the force measurement assembly in more than one direction.

8. The force measurement system according to claim 1, wherein the force measurement assembly is in the form of a force plate or platform.

9. The force measurement system according to claim 1, wherein the force measurement assembly is in the form of an instrumented treadmill.

11. The force measurement system according to claim 1, wherein the data processing device executes a calibration procedure, which is loaded thereon from a computer-readable medium, and determines inertial parameters of the force measurement assembly through the utilization of linear and/or rotational motion profiles applied to the force measurement assembly by a motion base disposed thereunder.

34. The force measurement system according to claim 11, wherein the inertial parameters of the force measurement assembly comprise the mass of the assembly, the rotational inertia of the assembly, and the position vector of the center of gravity of the assembly, and wherein the mass of the assembly is computed as a function of the output forces and the acceleration measured by the at least one accelerometer.

10. (canceled)

12. (canceled)

13. (canceled)

14. A force measurement system having inertial compensation, the force measurement system comprising:

a force measurement assembly configured to receive a subject, the force measurement assembly including;

a surface for receiving at least one portion of the body of the subject;

at least one force transducer, the at least one force transducer configured to sense a measured quantity and output a signal that is representative of forces and/or moments being applied to the surface of the force measurement assembly by the subject;

at least one accelerometer configured to measure the acceleration of the force measurement assembly; and

a data processing device operatively coupled to the at least one force transducer and the at least one accelerometer of the force measurement assembly, the data processing device being configured to execute a calibration procedure that is loaded thereon from a computer-readable medium, and to determine inertial parameters of the force measurement assembly, which include the mass of the force measurement assembly, by utilizing the measured acceleration of the force measurement assembly while a plurality of linear and/or rotational motion profiles are applied to the force measurement assembly by a motion generating source external thereto;

wherein the data processing device is configured to receive the signal that is representative of the forces and/or moments being applied to the surface of the force measurement assembly by the subject, and to convert the signal into output forces and/or moments, the data processing device further being configured to compute the mass of the force measurement assembly as a function of the output forces and the acceleration measured by the at least one accelerometer; and

wherein the data processing device is further configured to utilize the determined inertial parameters of the force measurement assembly, which include the mass of the force measurement assembly, and the acceleration measured by the at least one accelerometer for correcting the output forces and/or moments so as to improve the measurement accuracy of the forces and/or moments being applied to the surface of the force measurement assembly by the subject.

17. The force measurement system according to claim 14, wherein the force measurement assembly further comprises at least one angular velocity sensor configured to measure the angular velocity of the force measurement assembly.

18. The force measurement system according to claim 17, wherein the data processing device is configured to use the acceleration and the angular velocity measured by the at least one accelerometer and the at least one angular velocity sensor, respectively, to compute inertial forces and moments, and to correct the output forces using the computed inertial forces and/or to correct the output moments using the computed inertial moments.

19. The force measurement system according to claim 18, wherein the data processing device computes the inertial moments as a function of the angular velocity measured by the at least one angular velocity sensor, and as a function of an angular acceleration of the force measurement assembly.

20. The force measurement system according to claim 14, wherein the at least one force transducer comprises a plurality of force transducers for sensing measured quantities that are representative of multi-dimensional forces and moments being applied to the surface of the force measurement assembly by the subject.

21. The force measurement system according to claim 20, wherein the at least one accelerometer comprises a plurality of accelerometers so as to enable multi-axis acceleration of the force measurement assembly to be determined, thereby compensating for the movement of the force measurement assembly in more than one direction.

22. The force measurement system according to claim 14, wherein the force measurement assembly is in the form of a force plate or platform.

23. The force measurement system according to claim 14, wherein the force measurement assembly is in the form of an instrumented treadmill.

35. The force measurement system according to claim 14, wherein the inertial parameters of the force measurement assembly further comprise the rotational inertia of the assembly and the position vector of the center of gravity of the assembly.

37. The force measurement system according to claim 18, wherein the at least one angular velocity sensor comprises a multi-component angular velocity sensor that is capable of measuring angular velocities of the force measurement assembly about multiple rotational axes.

38. The force measurement system according to claim 37, wherein the data processing device computes the inertial moments as a function of the angular velocities measured by the multi-component angular velocity sensor, and as a function of an angular acceleration of the force measurement assembly.

39. The force measurement system according to claim 38, wherein the data processing device computes the angular acceleration of the force measurement assembly by solving a plurality of kinematic equations using the acceleration and the angular velocity measured by the at least one accelerometer and the at least one angular velocity sensor, respectively.

15. (canceled)

16. (canceled)

24. A force measurement system having inertial compensation, the force measurement system comprising:

a force measurement assembly configured to receive a subject, the force measurement assembly including;

a surface for receiving at least one portion of the body of the subject;

at least one force transducer, the at least one force transducer configured to sense a measured quantity and output a signal that is representative of forces and/or moments being applied to the surface of the force measurement assembly by the subject;

at least one linear accelerometer configured to measure a linear acceleration of the force measurement assembly;

a motion base, which includes a plurality of actuators, operatively coupled to the force measurement assembly, the motion base configured to both displace and rotate the force measurement assembly in multiple dimensions; and

a data acquisition and processing device operatively coupled to the force measurement assembly, the data acquisition and processing device configured to acquire receive the signal that is representative of the forces and/or moments being applied to the surface of the force measurement assembly by the subject and to convert the signal into output forces and/or moments, the data acquisition and processing device being configured to receive the linear acceleration measured by the at least one linear accelerometer, and the data acquisition and processing device further being configured to use the linear acceleration measured by the at least one linear accelerometer to compute inertial forces, and to determine corrected externally applied forces by computing the mathematical difference between the computed inertial forces and the output forces so as to improve the measurement accuracy of the forces and/or moments being applied to the surface of the force measurement assembly by the subject.

25. The force measurement system according to claim 24, wherein the force measurement assembly further comprises at least one angular velocity sensor configured to measure the angular velocity of the force measurement assembly.

28. The force measurement system according to claim 24, wherein the at least one force transducer comprises a plurality of force transducers for sensing measured quantities that are representative of multi-dimensional forces and moments being applied to the surface of the force measurement assembly by the subject.

29. The force measurement system according to claim 28, wherein the at least one accelerometer comprises a plurality of accelerometers so as to enable multi-axis acceleration of the force measurement assembly to be determined, thereby compensating for the movement of the force measurement assembly in more than one direction.

30. The force measurement system according to claim 24, wherein the force measurement assembly is in the form of a force plate or platform.

31. The force measurement system according to claim 24, wherein the force measurement assembly is in the form of an instrumented treadmill.

32. The force measurement system according to claim 24,

wherein the data acquisition and processing device executes a calibration procedure, which is loaded thereon from a computer-readable medium, and determines inertial parameters of the force measurement assembly through the utilization of linear and/or rotational motion profiles applied to the force measurement assembly by the motion base;

and wherein the inertial parameters of the force measurement assembly include the mass of the force measurement assembly, the mass of the force measurement assembly being computed as a function of the output forces and the acceleration measured by the at least one accelerometer.

33. The force measurement system according to claim 25, wherein

the data acquisition and processing device is further configured to use the angular velocity measured by the at least one angular velocity sensor to compute inertial moments, and the data acquisition and processing device is configured to determine corrected externally applied moments by computing the mathematical difference between the computed inertial moments and the output moments, so as to improve the measurement accuracy of the moments being applied to the surface of the force measurement assembly by the subject.

40. The force measurement system according to claim 33, wherein the data acquisition and processing device computes the inertial moments as a function of the angular velocity measured by the at least one angular velocity sensor, and as a function of an angular acceleration of the force measurement assembly.

41. The force measurement system according to claim 40, wherein the data acquisition and processing device computes the angular acceleration of the force measurement assembly by solving a plurality of kinematic equations using the acceleration and the angular velocity measured by the at least one accelerometer and the at least one angular velocity sensor, respectively.

26. (canceled)

27. (canceled)

36. (canceled)